Smooth or merge the hand and the forearm
Since user hawkenfox suggested it, I will post my comment as an answer:

You need to Tab into Edit Mode, RClick to select a vertex on the hand, press Ctrl L to select all the connected (Linked) geometry, then H to Hide the hand geometry. This will let you see what's going on with the arm underneath and you can select then delete the faces of the arm stump. Then Alt H to un-Hide. Repeat this for the arm and delete the faces on the wrist of the hand geometry. Then you can use Merge (Alt M) or Fill (F) to connect the hand to the forearm. Whether modeling in Blender or Sculptris, it's better if you can sculpt all as one piece in the future and avoid this extra work.